Results are presented on the function and use of the catalyst in the c
ommonly employed high-temperature catalytic oxidation (HTCO) method fo
r determination of organic carbon concentrations, The instrument used
was a Shimadzu TOC 5000 analyzer with a 0.5% platinum-coated aluminum
oxide catalyst, Some basic considerations on gas flow rates and volume
s of the catalyst kiln, together with experiments using carrier gas wi
th and without oxygen, led to the conclusion that O-2 is unlikely as t
he source of reacted oxygen in the HTCO oxidation of organic carbon. R
esults from injections of C-14-labelled organic material showed that n
o residual carbon remains on the catalyst surface after a large number
of injections, This indicates that the oxidation of organic carbon to
gaseous compounds is complete and the catalyst is not a source of car
ry over signal between injections. The blank signal from injection of
water probably originates from carbonaceous compounds contained in the
catalyst particles. A series of salt water injections (salinity 34.4)
showed that > 2500 injections can be made without deterioration of ca
talyst performance.